Systems and methods for generating customized control boundaries

ABSTRACT

A method includes providing a standard control boundary defining a portion of a bone to be resected, registering a position of a soft tissue at the bone, obtaining a customized control boundary by moving a vertex of the standard control boundary based on the position of the soft tissue, and controlling a robotic device to constrain operation of a cutting tool to an area defined by the customized control boundary.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/451,105, filed Mar. 6, 2017, which is a continuation of U.S.application Ser. No. 14/578,064, filed Dec. 19, 2014, which claims thebenefit of and priority to U.S. Provisional Application No. 61/922,740,filed Dec. 31, 2013, all of which are incorporated herein by referencein their entireties.

BACKGROUND

The present disclosure relates generally to force feedback systemsassociated with computer-assisted surgery (“CAS”) systems and, moreparticularly, to systems and methods for customizing interactive hapticboundaries associated with CAS systems based on patient-specificinformation.

The knee joint comprises the interface between the distal end of thefemur and the proximal end of the tibia. In a properly-functioning kneejoint, medial and lateral condyles of the femur pivot smoothly alongmenisci attached to respective medial and lateral condyles of the tibia.When the knee joint is damaged, the natural bones and cartilage thatform the joint may be unable to properly articulate, which can lead tojoint pain and, in some cases, interfere with normal use of the joint.

In some situations, surgery is required to restore normal use of thejoint and reduce pain. Depending upon the severity of the damage, thesurgery may involve partially or completely replacing the joint withprosthetic components. During such knee replacement procedures, asurgeon resects damaged portions of the bone and cartilage, whileattempting to leave healthy tissue intact. The surgeon then fits thehealthy tissue with artificial prosthetic components designed toreplicate the resected tissue and restore proper knee joint operation.

Typically, prior to the surgery, the surgeon develops a preliminary(“pre-operative”) plan that serves as a guide to performing the surgery.As part of the pre-operative planning, the surgeon surveys, among otherthings, the size, shape, kinematic function, and condition of thepatient's joint. Using computer-assisted surgery systems, this surveycan be performed by obtaining computer-based images of the joint andgenerating a computer-based model of the joint of the patient in virtualsoftware space. Using this virtual model, the surgeon can evaluate thecondition of the anatomic features of the joint and plan, among otherthings, the location and amount of bone that needs to be removed and theposition and orientation in which the prosthetic components should beimplanted on the bone to restore normal joint functionality.

Although the surgeon has a great degree of flexibility in customizingmost aspects of the surgery based on the unique anatomy of the patient,the surgeon is typically limited to selecting from among a finite numberof different prosthetic implant components. In many situations, asurgeon performs surgery on a patient whose anatomy does not preciselymatch any of the available prosthetic implant components. As a result,the surgeon may select a prosthetic implant that most closely fits—butdoes not precisely match—the patient's anatomy. The surgeon can thenmodify the surgical plan (either pre or intra-operatively) toaccommodate for the selected prosthetic components.

In some situations, the CAS system may include a force feedback controlsystem that is coupled to one or more surgical instruments (e.g.,cutting tools) and configured to provide force feedback for controllingthe surgical instrument during the surgery. The force feedback controlsystem may constrain the cutting tool to limit the position or operationof the surgical instrument to within certain predefined boundaries. Byallowing users to strategically define the placement of the virtualboundaries associated with the force feedback control system, these CASsystems enable surgeons to precisely and accurately control theresection and sculpting of the bone in preparation for receiving theprosthetic implant.

Because CAS systems provide a solution for accurately, reliably, andprecisely executing bone cuts by defining the boundaries at which acutting surface of a surgical instrument can operate, some CAS systemsnow include virtual software models that match the size and shape ofavailable prosthetic implants. The virtual software model of theimplant(s) can be positioned (in software) relative to the virtualmodel(s) of the patient's joint prior to or during the surgicalprocedure. Once positioned, the software model of the implant may be“registered” to the virtual model of the patient's anatomy so that thecutting surface is constrained to operate only within the area definedby the software model of the implant, limiting tissue removal only tothe specific area of the patient's bone associated with the registeredplacement of the implant.

Systems that provide virtual models, and corresponding hapticboundaries, associated with a selection of available implants may allowsurgeons to quickly and efficiently define a resection pattern forpreparing the bone to receive the implant. Generally, each virtualimplant model may be associated with a corresponding fixed hapticboundary, which may be based on the size and shape to the geometryassociated with the virtual implant model. However, in some situationsthe surgeon selects an undersized prosthetic implant, but nonethelesswishes to remove areas of diseased or damaged tissue that may be locatedbeyond the boundaries required to accommodate the undersized prostheticimplant.

SUMMARY

In accordance with one aspect, the present disclosure is directed to amethod for customizing a haptic boundary based on a patient-specificanatomy. The method may include identifying a standard haptic boundarybased on a geometry of a virtual implant model to be implanted on theanatomy. The method may also include identifying a reference featureassociated with a virtual implant model and determining an intersectionbetween the identified reference feature and a virtual model associatedwith an anatomy of the patient. An anatomic perimeter at theintersection between the identified reference feature and the virtualmodel of the anatomy may be identified and at least one anatomic featuremay be determined on the virtual model of the anatomy. The standardhaptic boundary may be modified based on the at least one anatomicfeature to generate a customized haptic boundary.

According to another aspect, the present disclosure is directed toanother method for method for customizing a haptic boundary based on apatient-specific anatomy. The method may include displaying a graphicalrepresentation of an implant in virtual coordinate space and displayinga graphical representation of a bone in the virtual coordinate space.The method may further include positioning the graphical representationof the implant relative to the graphical representation of the bonebased on a user input. The method may also include displaying agraphical representation of a standard haptic boundary based on thegeometry of the implant and extracting reference feature informationassociated with the graphical representation of the implant. An anatomicperimeter at an intersection between the extracted reference feature andthe graphical representation of the bone may be mapped, and at least oneanatomic feature on the graphical representation of the bone from theintersection of the reference feature and the graphical representationof the bone may also be mapped. The method may further include modifyingthe standard haptic boundary based on at least one anatomic feature togenerate a customized haptic boundary, and displaying a graphicalrepresentation of the customized haptic boundary in the virtualcoordinate space.

In accordance with yet another aspect, the present disclosure isdirected to a computer-assisted surgery system including a display, aninput device configured to receive data input by a user, and a processoroperatively coupled to the input device and the display. The processormay be configured to identify a standard haptic boundary based on ageometry of a virtual implant model to be implanted on the anatomy,identify a reference feature associated with a virtual implant model,and determine an intersection between the identified reference featureand a virtual model associated with an anatomy of the patient. Theprocessor may also be configured to identify an anatomic perimeter atthe intersection between the identified reference feature and thevirtual model of the anatomy and determine at least one anatomic featureon the virtual model of the anatomy from the intersection of thereference feature and the virtual model of the anatomy. The processormay also be configured to modify the standard haptic boundary based onat least one anatomic feature to generate a customized haptic boundary,and display the customized haptic boundary and the virtual modelassociated with the anatomy of the patient on the display.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments that,together with the description, serve to explain the principles andfeatures of the present disclosure.

FIG. 1 illustrates a perspective view of post-operative prosthetic kneejoint fitted with a prosthetic system;

FIG. 2 provides a schematic illustration of an exemplarycomputer-assisted surgery (CAS) system, in which certain methodsconsistent with the disclosed embodiments may be implemented;

FIG. 3 provides a schematic diagram of an exemplary computer system,which may be used in one or more components associated with the CASsystem illustrated in FIG. 2 ;

FIG. 4 illustrates an exemplary screen shot associated with a graphicaluser interface of the CAS system, in accordance with certain disclosedembodiments;

FIG. 5 illustrates a virtual representation of a standard hapticboundary for a tibial prosthetic component.

FIG. 6 illustrates a virtual representation of a custom haptic boundarybased on intersecting a plane with the bone model.

FIG. 7 illustrates a virtual representation of a customized hapticboundary in accordance with certain disclosed embodiments.

FIG. 8 provides a flowchart illustrating an exemplary method forgenerating customized haptic boundaries based on patient-specificanatomic data;

FIG. 9 illustrates a virtual representation of a step of generating acustomized haptic boundary in accordance with certain disclosedembodiments.

FIG. 10 illustrates a virtual representation of another step ofgenerating a customized haptic boundary in accordance with certaindisclosed embodiments.

FIG. 11 illustrates a virtual representation of another step ofgenerating a customized haptic boundary in accordance with certaindisclosed embodiments.

FIG. 12 illustrates a virtual representation of another step ofgenerating a customized haptic boundary in accordance with certaindisclosed embodiments.

FIG. 13 illustrates a virtual representation of another step ofgenerating a customized haptic boundary in accordance with certaindisclosed embodiments.

FIG. 14 provides a flowchart illustrating another exemplary method forgenerating a customized haptic boundary based on patient-specificanatomic data.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings.

A healthy knee joint comprises the interface between the distal end ofthe femur and the proximal end of the tibia. If the healthy knee jointbecomes damaged due, for example, to injury or disease, knee surgery maybe required to restore normal structure and function of the joint. Ifthe damage to the knee is severe, total knee arthroplasty (“TKA”) may berequired. TKA typically involves the removal of the damaged portion ofjoint and the replacement of the damaged portion of the joint with oneor more prosthetic components.

In some TKA procedures, one or more of cruciate ligaments (includinganterior cruciate ligament and/or posterior cruciate ligament) may beleft intact, to be re-used with the prosthetic implants to form the newknee joint. In these “cruciate-retaining” applications, the prostheticimplant components may be configured to avoid interference with orimpingement on the retained cruciate ligaments passing through theintercondylar area of the knee joint. For example, each of the femoraland tibial prosthetic components may be designed with a intercondylar“notch” that extends from the posterior of the prosthetic componenttoward the anterior of the prosthetic component. The femoral and tibialintercondylar notches provide a passage that allows the cruciateligament to pass from the femoral intercondylar fossa down to the tibialeminence.

Because cruciate ligaments are exposed to significant tensile forceduring normal knee joint use, it is important that the attachment siteswhere the cruciate ligaments attach to the femur and tibia havesufficient strength to properly anchor the cruciate ligaments to thebone. Otherwise, the force applied by the cruciate ligament strains thetissue around the attachment site, possibly leading to failure of thejoint, which may require corrective surgery to repair. One way to limitthe possibility of such a failure is to limit the amount of boneresected at or near the attachment site(s) (i.e., the intercondylarfossa of the femur and tibial emmence 101 a of the tibia). Limiting theamount of disturbance of native tissue at the attachment sites helpspreserve the natural anchoring mechanism of the tissue, which decreasesthe likelihood of failure at the attachment site.

In the embodiment illustrated in FIG. 1 , prosthetic implant system 110includes a number of components configured to replace a resected portionof a native knee joint. According to one embodiment, prosthetic implantsystem 110 includes a tibial implant system 120 configured to replace aresected portion of a native tibia 101. Prosthetic implant system 110also includes a femoral component 130 configured to replace a resectedportion of a native femur 102. After implantation during kneereplacement surgery, tibial implant system 120 and femoral component 130cooperate to replicate the form and function of the native knee joint.

Femoral component 130 is secured to the distal end of femur 102 andconfigured to replace the structure and function of the native femoralportion of knee joint 100. As such, femoral component 130 may bemanufactured from surgical-grade metal or metal alloy material (such assurgical-grade steel, titanium or titanium allow, a cobalt-chromiumalloy, a zirconium alloy, or tantalum) that is substantially rigid forproviding sufficient strength to support the forces required of the kneejoint. According to one embodiment, femoral component 130 may embody asingle component having a plurality of different structural features,each configured to perform a particular function associated with theknee joint 100. For example, femoral component 130 may include a pair ofcondyles 132, each of which is coupled to a patellar guide portion 133.The pair of condyles 132 are separated from one another by anintercondylar notch 138, which provides a channel through which one ormore cruciate ligaments 103, such as anterior cruciate ligament (ACL)103 a and/or posterior cruciate ligament (PCL) 103 b, may pass.

Tibial implant system 120 may include a plurality of components thatcooperate to provide a stable surface that articulates with femoralcomponent 130 to restore proper knee joint function. As illustrated inFIG. 1 , tibial implant system 120 includes a base portion 121 and oneor more insert portions 123. During a knee replacement procedure, baseportion 121 is secured to the proximal end of the tibia 101, which hasbeen surgically prepared by removing damaged bone and tissue andreshaping the healthy bone to receive the base portion 121. Once baseportion 121 is secured to tibia 101, the surgeon completes assembly oftibial implant system 120 by engaging and securing insert portions 123within base portion 121. Base portion 121 of tibial prosthetic systemmay be configured with a passage through the center to allow forconnection between the retained cruciate ligaments 103 and tibialeminence 101 a.

Base portion 121 may be configured to emulate the structure and functionof the top surface of tibia 101. Thus, similar to femoral component 130,base portion 121 may be manufactured from surgical-grade metal or metalalloy material (such as surgical-grade steel, titanium or titaniumallow, a cobalt-chromium alloy, a zirconium alloy, or tantalum) that issubstantially rigid for providing a stable base upon which toreconstruct the remainder of the prosthetic joint.

Insert portions 123 may be designed to emulate the form and function ofcertain components of the natural femorotibial interface, including,among other things, medial and lateral menisci of the knee joint. Assuch, insert portions 123 may be constructed of smooth, semi-rigidsynthetic or semi-synthetic plastic, rubber, or polymer material. Insertportions 123 may be configured to provide a smooth surface that isdesigned to articulate with a femoral component 130 during normal kneeoperation. According to one embodiment, insert portions 123 areconfigured to removably engage with base portion 121. Accordingly,insert portions 123 are configured for periodic replacement if insertportions 123 deteriorate over time due, for example, to excessive wear.

In order to ensure precise and accurate preparation of the joint toreceive a prosthetic implant, CAS system may be used to generate agraphical representation of the surgical site and a correspondingvirtual guide that may aid the surgeon in properly aligning the toolprior to interaction with patient's anatomy. Many CAS systems includesoftware that allows users to electronically register certain anatomicfeatures (e.g., bones, soft tissues, etc.), surgical instruments, andother landmarks associated with the surgical site. CAS systems maygenerate a graphical representation of the surgical site based on theregistration of the anatomic features. The CAS software also allowsusers to plan certain aspects of the surgical procedure, and registerthese aspects for display with the graphical representation of thesurgical site. For example, in a knee joint replacement procedure, asurgeon may register target navigation points, the location and depth ofbone and tissue cuts, virtual boundaries that may be associated with acorresponding reference for the application of haptic force, and otheraspects of the surgery.

FIG. 2 provides a schematic diagram of an exemplary computer-assistedsurgery (CAS) system 200, in which processes and features associatedwith certain disclosed embodiments may be implemented. CAS system 200may be configured to perform a wide variety of orthopedic surgicalprocedures such as, for example, partial or total joint replacementsurgeries. As illustrated in FIG. 2 , CAS system 200 includes a trackingsystem 201, computer-assisted navigation system 202, one or more displaydevices 203 a, 203 b, and a robotic system 204. It should be appreciatedthat CAS system 200, as well as the methods and processes describedherein, may be applicable to many different types of joint replacementprocedures. Although certain disclosed embodiments may be described withrespect to knee replacement procedures, the concepts and methodsdescribed herein may be applicable to other types of orthopedicsurgeries, such as partial hip replacement, full or partial hipresurfacing, shoulder replacement or resurfacing procedures, and othertypes of orthopedic procedures.

Robotic system 204 can be used in an interactive manner by a surgeon toperform a surgical procedure, such as a knee replacement procedure, on apatient. As shown in FIG. 2 , robotic system 204 includes a base 205, anarticulated arm 206, a force system (not shown), and a controller (notshown). A surgical tool 210 (e.g., an end effector having an operatingmember, such as a saw, reamer, or burr) may be coupled to thearticulated arm 206. The surgeon can manipulate the surgical tool 210 bygrasping and manually moving the articulated arm 206 and/or the surgicaltool 210.

The force system and controller are configured to provide control orguidance to the surgeon during manipulation of the surgical tool. Theforce system is configured to provide at least some force to thesurgical tool via the articulated arm 206, and the controller isprogrammed to generate control signals for controlling the force system.In one embodiment, the force system includes actuators and abackdriveable transmission that provide haptic (or force) feedback toconstrain or inhibit the surgeon from manually moving the surgical toolbeyond predefined virtual boundaries defined by haptic objects asdescribed, for example, in U.S. Pat. No. 8,010,180 and/or U.S. patentapplication Ser. No. 12/654,519 (U.S. Patent Application Pub. No.2010/0170362), filed Dec. 22, 2009, each of which is hereby incorporatedby reference herein in its entirety. According to one embodiment, CASsystem 200 is the RIO® Robotic Arm Interactive Orthopedic Systemmanufactured by MAKO Surgical Corp. of Fort Lauderdale, Florida. Theforce system and controller may be housed within the robotic system 204.

Tracking system 201 may include any suitable device or system configuredto track the relative locations, positions, orientations, and/or posesof the surgical tool 210 (coupled to robotic system 204) and/orpositions of registered portions of a patient's anatomy, such as bones.Such devices may employ optical, mechanical, or electromagnetic posetracking technologies. According to one embodiment, tracking system 201includes a vision-based pose tracking technology, wherein an opticaldetector, such as a camera or infrared sensor, is configured todetermine the position of one or more optical transponders (not shown).Based on the position of the optical transponders, tracking system 201may capture the pose (i.e., the position and orientation) information ofa portion of the patient's anatomy that is registered to thattransponder or set of transponders.

Navigation system 202 may be communicatively coupled to tracking system201 and may be configured to receive tracking data from tracking system201. Based on the received tracking data, navigation system 202 maydetermine the position and orientation associated with one or moreregistered features of the surgical environment, such as surgical tool210 or portions of the patient's anatomy. Navigation system 202 may alsoinclude surgical planning and surgical assistance software that may beused by a surgeon or surgical support staff during the surgicalprocedure. For example, during a joint replacement procedure, navigationsystem 202 may display images related to the surgical procedure on oneor both of the display devices 203 a, 203 b.

Navigation system 202 (and/or one or more constituent components of CASsystem 200) may include or embody a processor-based system (such as ageneral or special-purpose computer) in which processes and methodsconsistent with the disclosed embodiments may be implemented. Forexample, as illustrated in FIG. 3 , CAS system 200 may include one ormore hardware and/or software components configured to execute softwareprograms, such as, tracking software, surgical navigation software, 3-Dbone modeling or imaging software, and/or software for establishing andmodifying virtual haptic boundaries for use with a force system toprovide haptic feedback to surgical tool 210. For example, CAS system200 may include one or more hardware components such as, for example, acentral processing unit (CPU) (processor 231); computer-readable media,such as a random access memory (RAM) module 232, a read-only memory(ROM) module 233, and a storage device 234; a database 235; one or moreinput/output (I/O) devices 236; and a network interface 237. Thecomputer system associated with CAS system 200 may include additional,fewer, and/or different components than those listed above. It isunderstood that the components listed above are exemplary only and notintended to be limiting.

Processor 231 may include one or more microprocessors, each configuredto execute instructions and process data to perform one or morefunctions associated with CAS system 200. As illustrated in FIG. 3 ,processor 231 may be communicatively coupled to RAM 232, ROM 233,storage device 234, database 235, I/O devices 236, and network interface237. Processor 231 may be configured to execute sequences of computerprogram instructions to perform various processes, which will bedescribed in detail below. The computer program instructions may beloaded into RAM for execution by processor 231.

Computer-readable media, such as RAM 232, ROM 233, and storage device234, may be configured to store computer-readable instructions that,when executed by processor 231, may cause CAS system 200 or one or moreconstituent components, such as navigation system 202, to performfunctions or tasks associated with CAS system 200. For example, computerreadable media may include instructions for causing the CAS system 200to perform one or more methods for determining changes in parameters ofa knee joint after a knee arthroplasty procedure. Computer-readablemedia may also contain instructions that cause tracking system 201 tocapture positions of a plurality of anatomic landmarks associated withcertain registered objects, such as surgical tool 210 or portions of apatient's anatomy, and cause navigation system 202 to generate virtualrepresentations of the registered objects for display on I/O devices236. Exemplary methods for which computer-readable media may containinstructions will be described in greater detail below. It iscontemplated that each portion of a method described herein may havecorresponding instructions stored in computer-readable media for causingone or more components of CAS system 200 to perform the methoddescribed.

I/O devices 236 may include one or more components configured tocommunicate information with a user associated with CAS system 200. Forexample, I/O devices 236 may include a console with an integratedkeyboard and mouse to allow a user (e.g., a surgeon) to input parameters(e.g., surgeon commands 250) associated with CAS system 200. I/O devices236 may also include a display, such as monitors 203 a, 203 b, includinga graphical user interface (GUI) for outputting information on amonitor. I/O devices 236 may also include peripheral devices such as,for example, a printer for printing information associated with CASsystem 200, a user-accessible disk drive (e.g., a USB port, a floppy,CD-ROM, or DVD-ROM drive, etc.) to allow a user to input data stored ona portable media device, a microphone, a speaker system, or any othersuitable type of interface device. For example, I/O devices 236 mayinclude an electronic interface that allows a user to input patientcomputed tomography (CT) data 260 into CAS system 200. This CT data maythen be used to generate and manipulate virtual representations ofportions of the patient's anatomy (e.g., a virtual model of a tibia 101)in software.

Software associated with CAS system 200 may be configured to enablesurgical planning, navigation, and basic image guided surgerycapabilities. For example, software associated with CAS system 200 mayinclude computer-implemented processes for generating and displayingimages (either captured images or computer-generated captured images)from image data sets, computer-implemented processes for determining aposition of a tip and an orientation of an axis of a surgicalinstrument, and computer-implemented processes for registering a patientand an image data set to a coordinate frame of the tracking system 201.These processes may enable, for example, the CAS system 200 to displayon the display device(s) 203 a, 203 b a virtual representation of atracked surgical instrument (and/or a prosthetic implant) overlaid onone or more images of a patient's anatomy and to update the virtualrepresentation of the tracked instrument in real-time during a surgicalprocedure. Images generated from the image data set may betwo-dimensional or, in the case of a three-dimensional image data set, athree-dimensional reconstruction based, for example, on segmentation ofthe image data set. According to one embodiment, images associated withthe image data set may include CT scan data associated with a patient'sanatomy, a prosthetic implant, or any object. When more than one imageis shown on the display device(s) 203 a, 203 b, the CAS system 200 maycoordinate the representation of the tracked instrument among thedifferent images.

According to another embodiment, an imageless system may be utilized togenerate and manipulate virtual representations of portions of thepatient's anatomy (e.g., a virtual model of a tibia 101) in software.Imageless systems include technologies that are well-known in the art,such as systems utilizing statistically shaped models and methods ofbone morphing. In one form of imageless system, a virtual representationof a portion of the patient's anatomy is created based onpatient-specific characteristics (such as anatomic landmarks obtained byphysically touching the patient's anatomy using a probe tool). In otherimageless systems, a three-dimensional virtual representation of aportion of the patient's anatomy is obtained by selecting athree-dimensional model from a database or library of bone models. Theselected bone model can then be deformed based on patient-specificcharacteristics, creating a three-dimensional representation of thepatient's anatomy.

Processor 231 associated with CAS system 200 may be configured toestablish a virtual haptic geometry associated with or relative to oneor more features of a patient's anatomy. As explained, CAS system 200may be configured to create a virtual representation of a surgical sitethat includes, for example, virtual representations of a patient'sanatomy, a surgical instrument to be used during a surgical procedure, aprobe tool for registering other objects within the surgical site, andany other such object associated with a surgical site.

In addition to physical objects, CAS system 200 may be configured togenerate virtual objects that exist in software and may be useful duringthe performance of a surgical procedure. For example, CAS system 200 maybe configured to generate virtual boundaries that correspond to asurgeon's plan for preparing a bone, such as boundaries defining areasof the bone that the surgeon plans to cut, remove, or otherwise alter.Alternatively or additionally, CAS system 200 may define virtual objectsthat correspond to a desired path or course over which a portion ofsurgical tool 210 should navigate to perform a particular task.

Virtual boundaries and other virtual objects may define a point, line,or surface within a virtual coordinate space (typically defined relativeto an anatomy of a patient) that serves as a boundary at which hapticfeedback is provided to a surgical instrument when the tracked positionof the surgical instrument interacts with the virtual boundary orobject. For example, as the surgeon performs a bone cutting operation,tracking system 201 of CAS system 200 tracks the location of the cuttingtool and allows the surgeon to freely move the tool in the workspacewhile the virtual representation of the cutting tool is not proximate tothe haptic boundary. However, when the representation of the tool is inproximity to a virtual haptic boundary (that has been registered to theanatomy of the patient), CAS system 200 controls the force feedbacksystem to provide haptic guidance that tends to constrain the surgeonfrom penetrating the virtual haptic boundary with the cutting tool. Forexample, a virtual haptic boundary may be associated with the geometryof a virtual model of a prosthetic implant, and the haptic guidance maycomprise a force and/or torque that is mapped to the virtual boundaryand experienced by the surgeon as resistance to constrain tool movementfrom penetrating the virtual boundary. Thus, the surgeon may feel as ifthe cutting tool has encountered a physical object, such as a wall. Inthis manner, the virtual boundary functions as a virtual cutting guide.Accordingly, the force feedback system of CAS system 200 communicatesinformation to the surgeon regarding the location of the tool relativeto the virtual boundary, and provides physical force feedback to guidethe cutting tool during the actual cutting process. The force feedbacksystem of CAS system 200 may also be configured to limit the user'sability to manipulate the surgical tool.

Systems and methods consistent with the disclosed embodiments provide asolution for customizing a virtual haptic boundary and providing ahaptic feedback for guiding the surgical instrument. According to oneembodiment, the virtual haptic boundary may be customized based on auser request to modify a default boundary associated with acorresponding implant geometry. Alternatively or additionally, thevirtual haptic boundary may be customized based, at least in part, on adetection of the patient's anatomy (e.g., a location of soft tissue, theedge perimeter of a bone, etc.). The process for customizing the virtualhaptic boundary may be part of an implant planning phase, during whichthe surgeon pre-operatively or intra-operatively plans the placement ofprosthetic implants and the corresponding modification/removal of jointtissue to accommodate the implant. FIG. 4 provides an exemplary screenshot of a graphical user interface associated with planning software forCAS system 200.

FIG. 4 illustrates an exemplary screen shot 400 associated with agraphical user interface screen of planning software associated with CASsystem 200. As illustrated in FIG. 4 , planning software may includevirtual models of prosthetic implants, such as a tibial base portion 121associated with tibial implant system 120. According to one embodiment,a virtual implant model may be provided by the manufacturer of theprosthetic implant and may provide a graphical representation of thegeometry of the prosthetic implant. Using the graphical representationof the geometry, a virtual haptic boundary may be created and associatedwith the virtual implant model.

The graphical user interface 400 may include a plurality of sub-screens,each of which is configured to display a particular feature of theimplant planning. For example, graphical user interface 400 may includea first sub-screen (e.g., upper left) for displaying the selectedvirtual implant model (e.g., a model associated with tibia base portion121). Graphical user interface 400 may include a second sub-screen(upper right) for displaying the virtual model associated with thepatient's anatomy (e.g., tibia 101) upon which the implant will bepositioned. Graphical user interface 400 may include a third sub-screen(lower left) for displaying the planned placement of virtual implantmodel within the patient's anatomy. Graphical user interface 400 mayalso include a fourth sub-screen (lower right) for displaying a view ofrespective medial and lateral resection portions 401 a, 401 b associatedwith the planned implant placement. It is contemplated that the numberand view of sub-screens may differ from those provided in the exemplaryembodiment illustrated in FIG. 4 . It is also contemplated that one ormore of the sub-screens allow a user to interactively update the viewand/or the components within the view. For example, although the lowerright screen shows a top view of the simulated resection of thepatient's tibia 101 based on the planned implant placement shown in thelower left sub-screen, it is contemplated that the user can selectdifferent views (e.g., front, back, side, bottom, etc.) for displayingthe contents of the sub-screen.

During the implant planning stage, a surgeon or medical professional mayuse planning software associated with CAS system 200 to plan theplacement of prosthetic implants onto or within a patient's anatomy. Assuch, virtual (i.e., software) 3-D models of prosthetic implants, thepatient's anatomy, a surgical instrument (such as cutting tool(s)), andany other physical object that may be used during the surgical proceduremay be generated and registered to a virtual coordinate space (generallyone that corresponds with the patient's anatomy). Using planningsoftware, the surgeon can virtually position a prosthetic implantrelative to the patient's anatomy. Based on the virtual prostheticimplant model, the planning software may generate a standard hapticboundary 12. As depicted in FIG. 5 , the standard haptic boundary 12 maybe configured to accommodate the cutting profile and size of a cuttingtool, shown schematically as cutting tool 10. However, as shown, thestandard haptic boundary 12 based on the virtual implant model mayunder-resect or over-resect the actual bone area 11 necessary forresection to receive the implant. Over-resection risks damaging softtissue, such as collateral ligaments in the knee joint, whileunder-resecting may leave unresected bone that might require snapping orcracking off and/or manual trimming off with a rongeur. A hapticboundary 12 that is tied to the boundary 16 of the intersection 11 of areference plane of the implant model on the bone model, though, may beunable to accommodate the size and shape of the cutting tool 10 in someareas, as depicted in FIG. 6 . A cutting tool, such as an oscillatingsaw blade, has a wide effective shape that will not likely fit into theirregular geometry of the custom haptic perimeter shown in FIG. 6 .

FIG. 7 depicts a customized haptic boundary 18 that is based on theconfiguration of the standard haptic boundary 12, and that alsoaccommodates certain anatomic features 20 at the perimeter 16 of theintersection 11 of the patient bone and an implant reference surface.The customized haptic boundary 18 can therefore accommodate the cuttingtool 10, and also more closely matches the necessary areas for boneremoval to minimize under-resecting or over-resecting the bone. Thegeneration of the customized haptic boundary 18 is described in detailwith respect to the descriptions of FIGS. 8-14 below.

FIG. 8 provides a flowchart 800 that illustrates an exemplary method forautomatically generating a patient-specific virtual haptic boundary.According to one embodiment, the method illustrated in FIG. 8 may beimplemented during an implant placement planning stage associated withthe performance of a surgical procedure. The planning stage may beperformed pre-operatively by a surgeon or other medical professional,prior to commencement of the surgical procedure. Alternatively oradditionally, the planning stage may be performed (or repeated)intra-operatively, during the medical procedure.

As illustrated in flowchart 800 of FIG. 8 , once the virtual implantmodel has been placed in a desired position relative to the patient'sanatomy, the method commences by identifying a standard haptic boundary12 based on the size and shape of the implant model 13 associated withthe implant being used, the shape of the cutting tool, and the approachangle of the cutting tool (step 810). This standard haptic boundary 12typically corresponds closely with the geometric shape of the prostheticimplant. According to one embodiment, however, it may differ slightlyfrom the geometry of the implant. For example, the standard hapticboundary may be slightly larger than the prosthetic implant to allowsufficient space for surgical tool 10 access (e.g., to accommodate forthe width of a cutting tool) or to provide an area for entering thevolume defined by the virtual haptic boundary. The standard hapticboundary 12 is preferably a pre-determined haptic tied to the implantmodel, requiring no new haptic generation. A standard haptic boundary 12is shown in relation to a virtual model of the anatomy, such as virtualbone model 14 of the proximal end of the tibia in FIG. 9 .

Once the standard haptic boundary 12 is identified, the position andorientation of a reference feature 15 associated with the virtualimplant model in the virtual coordinate space is identified (step 820).The reference feature 15 of the virtual implant model may embody one ormore points, lines, planes, or surfaces of the virtual implant modeland, by extension, the prosthetic model associated therewith. Thereference feature 15 may be a reference plane a top, bottom, or othersurface of the implant model, or plane that is otherwise associated withthe implant model. In the embodiment of FIG. 10 , the reference feature15 is a plane shown relative to the virtual bone model 14. Alternativelyor additionally, the reference feature 15 may include or embody anyfeature associated with the implant that the surgeon wishes to use asthe reference with which to customize virtual haptic boundaries.

Once the reference feature 15 associated with the virtual implant model13 has been established, an intersection between the identifiedreference feature 15 and virtual model 14 of the patient's anatomy maybe determined (step 830). The intersection between the reference feature15 and the virtual model 14 of the patient's anatomy identifies apatient-specific anatomic perimeter 16 (step 840), as shown in FIG. 11 .

Upon determining the anatomic perimeter 16, planning software associatedwith CAS system 200 may be configured to identify certain features thatare specific to the patient's anatomy (step 850). As shown in FIG. 12 ,the anatomic features 20 are identified on the anatomic perimeter 16.The anatomic features 20 may include, for example, a most mediallandmark, most posterior-medial landmark, most posterior-laterallandmark, and most lateral landmark.

As an alternative or in addition to automatic detection, informationindicative of anatomic features 20, including a modification to theidentified anatomic features, may be received based on a user input. Forexample, a surgeon may designate one or more points, lines, or areas ofthe patient's anatomy as anatomic landmarks manually by physicallytouching the points, lines, or areas of the patient's anatomy using aprobe tool that has been registered with the virtual coordinate space.According to another embodiment, a user of CAS system 200 may inputinformation associated with anatomic landmarks using a graphical userinterface associated with planning software. Specifically, a user mayselect, via a graphical user interface, one or more points, lines,surfaces, or areas on a virtual model 14 of the patient's anatomy, or onthe anatomic perimeter 16, using a mouse or other input device. Forexample, protruding osteophytes on the patient anatomy mayunintentionally create computer generated landmarks outside of thedesired cutting region. The surgeon could then deselect this landmarkusing a navigated probe tool or by deselecting the landmark on a virtualmodel using a graphical user interface.

As depicted in FIG. 13 , once the anatomic features 20 are identified onthe virtual model 14 of the anatomy and/or the anatomic perimeter 16,planning software associated with the CAS system 200 may be configuredto modify the standard haptic boundary 12 based on the anatomic features20 (step 860). The standard haptic boundary 12 may be stretched orshrunk to more closely match the anatomic perimeter 16. In certainembodiments, only the edges of the standard haptic boundary 12 can bemoved based on simple formula percentages. Also the particular geometrycan be locked if necessary to prevent disfiguration of the implantshape. In other exemplary embodiments, the standard haptic perimeter 12may be composed of a series of simples lines or edges made up ofvertexes. Each vertex may be designated to stretch in only certaindirections, to not stretch (i.e. remain fixed), or to not stretch morethan a specified amount. For example, the medial edge vertexes of astandard haptic boundary 12 for a tibial component can be designated toonly move/stretch medial-lateral and to move/stretch together as agroup, so as to maintain the basic shape. Control of the adaptability ofthe vertexes helps to ensure that the customized haptic boundary 18maintains a shape that can accommodate the cutting tool 10.

Alternatively or additionally, the step of modifying the haptic boundary12 may be performed as a manual process by a surgeon. For example, afterthe anatomic perimeter 16 has been identified and/or the anatomicfeatures 20 have been determined (either automatically by the planningsoftware or manually by the surgeon), the surgeon may modify thestandard virtual haptic boundary 12 that was previously established, orthe automatically established customized haptic boundary 18. Inparticular, a surgeon may input information associated with moving thehaptic boundary using a graphical user interface associated withplanning software. For example, a surgeon may wish to contract the inneredges of virtual haptic boundaries associated with a tibial componentbase portion to limit the operation of the cutting tool near the tibialeminence, and avoid the possibility of inadvertently damaging softtissues (e.g., ACL or PCL) that attach thereto. To do so, the surgeonmay select, via a graphical user interface, one or more boundaries orvertexes of the haptic boundary and apply a manipulation to stretch/movethe boundary, using a mouse or other input device.

In one embodiment, the surgeon sets a series of offset preferences forthe stretchable boundaries. For example, the surgeon may desire that thehaptic boundary be offset outwardly from the anatomic landmark by a setdistance to enable the cutting tool to cut outside the bone perimeterfor improved cutting efficiency. Conversely, the surgeon may desire toset the haptic boundary offset inwardly from the anatomic landmark by aset distance to conservatively protect soft tissues.

Once generated, the customized haptic boundary may be registered to thepatient's anatomy and displayed on display of CAS system 200.Specifically, when the customized virtual haptic boundary 18 isgenerated, planning software associated with CAS system 200 may beconfigured to map the virtual surfaces and features that define thecustomized virtual haptic boundary 18 to the virtual coordinate spaceassociated with the patient's anatomy. As such, the boundary surfacesassociated with the customized virtual haptic boundary 18 become linkedto the patient's anatomy, thereby defining the areas of the patient'sanatomy within which the surgical instrument is permitted to operate. Byregistering the customized virtual haptic boundary 18 to the patient'sanatomy, the customized virtual haptic boundary 18 becomes virtuallylinked to the patient's anatomy, so that the customized virtual hapticboundary 18 can be tracked (and viewed) relative to the specificmovements, modifications, and adjustments in the patient's anatomyduring the surgical procedure. CAS system 200 may then apply the virtualhaptic boundary to surgical instrument.

FIG. 14 provides a flowchart showing another exemplary method 1400 forcustomizing a haptic boundary based on patient-specific parameters. Asillustrated in FIG. 14 , the method commences upon receipt ofpre-operative image(s) or image data associated with a patient's anatomy(step 1405). Pre-operative image(s) may include any two- orthree-dimensional image data set obtained using any suitable imagingprocess for recording images associated with a patient's anatomy suchas, for example, x-ray, computed tomography (CT), magnetic resonance(MR), positron emission tomography (PET), single photon emissioncomputed tomography (SPECT), ultrasound, etc. According to oneembodiment, I/O devices 236 of CAS system 200 may receive pre-operativeCT scan data 260 associated with the anatomy of the specific patientthat is to be operated on.

Upon receiving pre-operative image of the anatomy of a patient, softwareassociated with CAS system 200 generates a 3-D virtual model of thepatient's anatomy (step 1410). For example, CAS system 200 may includeone of a number of different software tools for rendering 3-D models ofobjects, based on the received 2-D (or 3-D) image data sets associatedwith the anatomy of the patient. In an alternative embodiment, the 3-Dvirtual model of the patient's anatomy is generated utilizing animageless system.

After the virtual model 14 of the patient's anatomy is generated, it maybe registered with the actual anatomy of the patient so that CAS system200 can virtually track the position and orientation of the actualanatomy of the patient in virtual software space. According to oneembodiment, this registration process involves associating a pluralityof points of the patient's anatomy with corresponding points on thevirtual model. Such associations can be made using a probe tool that hasbeen registered in the virtual coordinate space, whereby a plurality ofpoints on the patient's anatomy gathered by touching or “exploring” oneor more surfaces of the patient's anatomy using the tip of the probetool. Once the virtual model 14 is registered with the patient'sanatomy, CAS system 200 may be able to track the position andorientation of the patient's anatomy in the virtual coordinate space.

After the 3-D virtual model 14 of the patient's anatomy is generated andregistered to the patient's bone, planning software of CAS system 200facilitates the planning of an prosthetic implant within the patient'sanatomy (step 1415). Specifically, planning software of CAS system 200determines, based on a user input, placement of a virtual implant model13 relative to the virtual model 14 of the patient's anatomy. Forexample, a surgeon may select a virtual implant model 13 (e.g., virtualmodel associated with tibial base portion 121 as shown in FIG. 4 ) froma database of implants available for the surgery. Using a graphical userinterface 400, the surgeon may manipulate the position of the virtualimplant model 13 relative to the patient's anatomy (e.g., tibia 101),which produces a virtual representation of the tibia fitted with thevirtual implant, as shown in the lower left sub-screen of graphical userinterface 400 of FIG. 4 . Such a process for virtually planning implantplacement allows the surgeon to make precise adjustments to the positionof the implant relative to the patient's anatomy in a simulated softwareenvironment, prior to commencing the bone resection process.

Once the placement of the virtual implant model 13 with respect to thevirtual model 14 of the patient's anatomy is finalized, a standardhaptic boundary 12 is generated (step 1420). The standard hapticboundary 12 may correspond closely with the geometric shape of theprosthetic implant. Reference feature 15 information is extracted fromthe virtual implant model 13 (step 1425). According to one embodiment,the reference feature 15 of the virtual implant model may embody one ormore points, lines, planes, or surfaces of the virtual implant model 13.As illustrated in the embodiments described above, the reference feature15 is a plane associated with the implant model 13. Alternatively oradditionally, the reference feature 15 may include or embody any featureassociated with the implant that the surgeon wishes to use as thereference with which to customize virtual haptic boundaries. Forexample, reference feature 15 may include any surface associated withthe virtual implant model 13 that directly abuts or faces a surface ofthe virtual model 14 associated with the patient's anatomy.

Upon extracting the reference feature information, planning softwareassociated with CAS system 200 maps the reference feature informationonto the coordinate space of the patient's anatomy (step 1430). That is,planning software associated with CAS system 200 registers the referencefeatures 15 of the virtual implant model 13 to the virtual model 14 ofthe patient's bone, such that the reference surfaces 15 are trackedrelative to the position of the patient's bone.

Further referring to FIG. 14 , planning software of CAS system 200determines the intersection between the mapped reference surface 15 andthe patient's anatomy 14, and virtually resects tissue based on thedetermined intersection (step 1435). Planning software of CAS system 200may also be configured to modify the standard haptic boundary 12 togenerate a customized haptic boundary 18 (step 1440) based oninformation acquired during resection of the anatomy. As describedabove, the customized haptic boundary 18 may be generated bystretching/moving the standard haptic boundary 12 based upon at leastone anatomic feature 20 located on an anatomic perimeter 16, which isdefined by the intersection of the reference surface 15 and thepatient's anatomy 14. The identification of the anatomic features 20 maybe done automatically by the CAS system 200 or may be performed manuallyby the surgeon. Similarly, the modification of the standard hapticboundary 12 may be performed automatically based on the previouslyidentified anatomic features 20, or may be performed manually by thesurgeon who moves/stretches the boundary based on the patient specificanatomy or according to desired cutting approaches and techniques, i.e.to limit the operation of the cutting tool near the tibial eminence, andavoid the possibility of inadvertently damaging soft tissues (e.g., ACLor PCL) that attach thereto.

Upon generating the customized virtual haptic boundary 18, planningsoftware of CAS system 200 provides the user with an option to finalizethe virtual haptic boundary (step 1445). When the user decides tofinalize the virtual haptic boundary, CAS system 200 may update theforce system with the coordinates of virtual haptic boundary. As such,CAS system 200 selectively applies the virtual haptic forces to surgicalinstrument based on the tracked position of the surgical instrumentrelative to the virtual haptic boundary (step 1450).

The presently disclosed systems and methods for customizing virtualhaptic boundaries provide a solution for adjusting virtual hapticboundaries associated with force feedback control system forcomputer-assisted surgery systems. According to one embodiment, thissolution allows a user to modify a haptic boundary by stretching orcontracting an existing haptic boundary to fit one or more anatomiclandmarks. The planning software may then determine an intersectionbetween the stretched (or contracted) boundary and the virtual model ofthe patient's anatomy to define the location of the new virtual hapticboundary, and establish the new virtual haptic boundary based on thedetermined intersection.

The foregoing descriptions have been presented for purposes ofillustration and description. They are not exhaustive and do not limitthe disclosed embodiments to the precise form disclosed. Modificationsand variations are possible in light of the above teachings or may beacquired from practicing the disclosed embodiments. For example, thedescribed implementation includes software, but the disclosedembodiments may be implemented as a combination of hardware and softwareor in firmware. Examples of hardware include computing or processingsystems, including personal computers, servers, laptops, mainframes,microprocessors, and the like. Additionally, although disclosed aspectsare described as being stored in a memory, one skilled in the art willappreciate that these aspects can also be stored on other types ofcomputer-readable storage devices, such as secondary storage devices,like hard disks, floppy disks, a CD-ROM, USB media, DVD, or other formsof RAM or ROM.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed systems andassociated methods for customizing interactive haptic boundaries basedon patient-specific data. Other embodiments of the present disclosurewill be apparent to those skilled in the art from consideration of thespecification and practice of the present disclosure. It is intendedthat the specification and examples be considered as exemplary only,with a true scope of the present disclosure being indicated by thefollowing claims and their equivalents.

What is claimed is:
 1. A method, comprising: providing a standardcontrol boundary defining a portion of a bone to be resected;registering a position of a soft tissue at the bone; obtaining acustomized control boundary by moving a vertex of the standard controlboundary based on the position of the soft tissue; and controlling arobotic device to constrain operation of a cutting tool to an areadefined by the customized control boundary.
 2. The method of claim 1,further comprising providing a virtual representation of the bone. 3.The method of claim 2, further comprising displaying the standardcontrol boundary relative to the virtual representation of the bone andallowing a user to adjust the vertex of the standard control boundaryusing an input device.
 4. The method of claim 2, wherein providing thevirtual representation of the bone comprises generating the virtualrepresentation of the bone based on imaging of the bone.
 5. The methodof claim 2, wherein providing the virtual representation of the bonecomprises accessing a library of bone models.
 6. The method of claim 1,further comprising: selecting an implant component to be implanted onthe bone; and providing the standard control boundary based on theimplant component.
 7. The method of claim 1, wherein registering theposition of the soft tissue at the bone comprises tracking a probe. 8.The method of claim 1, wherein the cutting tool is coupled to therobotic device.
 9. The method of claim 1, wherein the bone to beresected is part of a shoulder of a patient.
 10. A computer-assistedsurgery system comprising: one or more processors; and non-transitorycomputer-readable media storing program instructions that, when executedby the one or more processors, perform operations comprising: providinga standard control boundary defining a portion of a bone to be resected;registering a position of a soft tissue at the bone; obtaining acustomized control boundary by changing a shape of the standard controlboundary, wherein changing the shape of the standard control boundarycomprises moving a vertex of the standard control boundary based on theposition of the soft tissue; and controlling a robotic device toconstrain operation of the cutting tool to an area defined by thecustomized control boundary.
 11. The computer-assisted surgery system ofclaim 10, wherein the operations further comprise providing a virtualrepresentation of the bone.
 12. The computer-assisted surgery system ofclaim 11, wherein the operations further comprise controlling a screento display the standard control boundary relative to the virtualrepresentation of the bone and adjusting the vertex of the standardcontrol boundary in response to user input.
 13. The computer-assistedsurgery system of claim 11, wherein providing the virtual representationof the bone comprise generating the virtual representation of the bonebased on imaging of the bone.
 14. The computer-assisted surgery systemof claim 11, wherein providing the virtual representation of the bonecomprises accessing a library of bone models.
 15. The computer-assistedsurgery system of claim 10, the operations further comprising:identifying an implant component to be implanted on the bone; andproviding the standard control boundary based on the implant component.16. The computer-assisted surgery system of claim 10 wherein registeringthe position of the soft tissue at the bone comprises obtaining dataindicative of positions of a tracked pose and registering the positionof the soft tissue using the data.
 17. The computer-assisted surgerysystem of claim 10, further comprising the robotic device and thecutting tool, the cutting tool coupled to the robotic device.
 18. Thecomputer-assisted surgery system of claim 10, wherein the bone to beresected is part of a shoulder of a patient.
 19. A surgical systemcomprising: an articulated arm; an actuator operable to provide a forceto the articulated arm; and a controller configured to control theactuator by: providing a standard control boundary based on a selectedimplant; obtaining a customized control boundary by moving an edge orvertex of the standard control boundary based on a position of a softtissue; and controlling the actuator based on a relationship between atracked tool and the customized control boundary.
 20. The surgicalsystem of claim 19, wherein a pose of the customized control boundary isdefined relative to a shoulder of a patient.